Free piston engine compressed air accumulator, variable volume



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lNvETaR ATTORNEY 3 2 w u m m w m m. 4, mw IU.. 1R N 2 e E 6 V w m 2 v unn. Q mw mw @l w .www RWL .G Emu BEM QM G n y n www O u? m BC A E n mFiled Nov. 2, 1945 UZMMA ll/M ATTORNEY Patented Get. 26,1948

FREE PISTON ENGINE COMPRESSED AIR ACCUMULATOR, VARIABLE VOLUME RobertHuber, Paris, France, assignor to Raul Pateras Pescara, Lisboa, PortugalApplication November'Z, 1945, Serial No. 626,249 In France November 18,1944 13 Claims. i

The present invention relates to free piston machines including, on theone hand, a movable system comprising amotor piston working in a motorcylinder, and, on the other hand, at least one gas cushion acting asaccumulator of energy for ensuring the return stroke of said movablesystem, and disposed, at least partly, behind the end Wall of saidpiston.

The invention is more especially, although not exclusively, concerned,among these .machines with free piston motor-compressors orauto-generators, i. e. machines of the kind above referred to includingat least one motor cylinder and one compressor cylinder and in which thecompressed air that is obtained is delivered to the receiver machines orelements either directly (case` of motor-compressors), or after havingpassed, at least partly, through the motor cylinder (case ofauto-generators) The chief object of the present invention is pistonauto-generator made according to the' present invention;

Figs. 2 to 4 inclusive are partial similar views l of threemodifications;

Fig. is a diagrammatic axial sectional View of a part of amotor-compressor having opposed free pistons and two stages ofcompression.

Supposing the invention to be applied to an auto-generator, as shown byFigs.' 1 to 4 inclusive by way of example, this machine includes a motorcylinder I surrounded by an air reservoir 2 and provided with inletports 3 and exhaust ports Il, opened by motor piston 5 when the latteris at the end of its outward stroke. A fuel injector 6 is tted in theend wall of cylinder I and this injector is fed from an injection pumpl. The motor piston is rigid with a compressor piston 8 of a diameterlarger than that of said motor piston, said compressor piston coactingwith a cylinder 9 and carrying a rod I0 for operating injection pump 7.

Cylinder 9 islimited, on the side of reservoir 2, by an annularpartition II, and on the opposite side by an end wall I2. The variablevolume chamber formed between the inner face of compressor piston 8 andpartition I I is provided with at least one suction valve I4 and atleast one discharge valve I3, the latter advantageously provided inpartition II. Thus the air compressed during the return or inward strokeof movable system 5, 8 by the inner face of piston 8 .is delivered intoreservoir 2, after which it passes, through inlet port 3, into motorcylinder I, while a mixture constituted by the combustion gases and theexcess of air under pressure escapes through portsi (see the arrows ofFig. ll this mixture constituting the gas under pressure to be deliveredby the auto-generator.

Concerning the cushion of the energy accumulator which ensures thereturn of the movable system toward the end of its inward stroke, andwhich operates for instance by compression of the air it contains duringthe outwardstroke of the movable system and expansion of said air duringthe return stroke, it is housed at least partly inside motor piston 5,which is made hollow for this purpose, whereby the air cushion is incontact with the hottest portions, in particular the crown, of thispiston.

According to the invention, in order to obtain a flow of air along theseportions, even during the periods for which the aircushi'on is out ofcommunication with the outside (for instance during the periodscorresponding to stable working conditions, for which it is notnecessary to adjust the weight of air present inside the cushion bymeans of known adjustment means not shown by the drawing) the inside ofsaid air cushion is divided into two parts, the ratio of the respectivevolumes of which varies during the working of the piston, the volume ofone of these portions being for instance of constant volume while thevolume of the other portion varies as a. consequence of the movements ofmovable system 5, ti, 'a passage of restricted section being providedbetween these two portions. The means for dividing the air cushion intosaid two portions and forming the passage of restricted section,preferably located close to the crown thereof are constituted by abaille provided inside said cushion.

In the' embodiment of Fig. 1, the air cushion is housed in the portion aof compressor cylinder 9 located on the outer side of piston 8, thespace b inside said piston, and the space c inside the f motor piston 5.

According to the embodiment of Fig. 1, the bale is constituted by apartition tI5, located on the inside' of motor piston '5 and close tothe crown 5a thereof. The portions of the cushion above referred to arehoused on' the one hand, in

spaces a, b and most of the volume of space c,

The first of these portions is of variable volume and the other oiconstant volume.

Furthermore, I provide, in said partition il, holes i6 which constitutethe 'passage of restricted section between the two parts in question.

Finally, according to an advantageous arrangeinent, partition i isutilized for the fixation of the piston crown la to piston` I. For thispurlwse, a housing ila is provided at the center of this partition, foraccommodating two half-sockets i1, of U-shaped axial section, adapted tohold together two disc-shaped parts Il, lo respectively rigid with crown5a and abolt 2U, the whole beingv kept in position by a spring 2|interposed between the. bottom wall of housing lia and a nut 22 carriedby the end ofsaid bolt.

When the machine is in operation, a part of the air present in thevariable volume portion of the air cushion (spaces a, b and most oi' c)enters chamber c.. through holes I6 when movable system 5, 8 is movingoutwardly, while the air stream through holes i6 takes place in theopposed direction during the inward strokes of said system. I thusobtain a constant renewal of the air present in chamber 8a and,consequently, an eillcient cooiing of the piston end.

Figs. 2, 3 and 4 relate to modications of the auto-generator shown byFig. 1.

According to these embodimentsthe baille provided on the inside of motorpiston 5 is constituted by a tube 23 the outer diameter of which issmaller than the inner diameter of motor piston 5, whereby Van annularspace cs is left between said tube and the wall of said piston. Thistube 23 is flxed to the outer face of compressor piston 8, so that thecommunication between compartment a and space cb is through the insideoi said tube, which extends to a short distance from the crown 5b ofpiston 5, which is iltted, opposite the free end of tube 23, with iins24.

The passage of restricted section which is to constitute thecommunication between the variable volume portion and the constantvolume portion of the air cushion is constituted, in the embodiments ofFigs. 2 to 4, according to the dimensions chosen, either by the insideof tube 2 3, or

vby the interval 4left between the free edge of this tube and the crown5b of piston 5 provided with fins which considerably restrict thesection of passage. In both cases, I obtain, as a consequence of themovements of the movable system, a cooling gas stream inside motorpiston 5 along the end wall thereof and the portions adjoining it.

The rate of flow of this stream depends upon the ratio of the constantvolume portion to the variable volume portion. The higher this ratio,the more intensive this gas stream.

In the embodiment of Fig. 2, the constant volume portion is housed inspace b inside the compressor piston 8 and space ce inside motor piston5 between the inner wall thereof and the outer wall of tube 23, thecommunication between these two spaces being ensured by holes 25,whereas the variable volume portion is housed in space a and the insideci of tube 23. vThus a high ratio is obtained between the two portionsin question, and, consequently, an intensive cooling stream.

In the embodiment of Fig. 3, the two portions in question are housed inspace cb on the one hand and spaces q, b and ci on the other hand. Thisratio is therefore smaller and the cooling stream less intensive'than inthe embodiment of Fig. 2.

In the embodiment of Fig. 4, the two portions e 4 in question are housedin space cs on the one hand and spaces a, b, ci and cb" on the other Yin the embodiment of Fig. 4, into two partial spaces cb' and cb", thelatter being in communication, through holes 21, with the variablevolume part. The ratio above referred to and the intensity of thecooling stream are, in the embodiment of Fig. 4, stili lower than inthat of Fig. 3.

It results from Figs. 2 to 4 that it is easy to determine, throughsuitable means, the ratio of the constant volume portion to the variablevolume portion, and consequently the intensityof the cooling stream.

Concerning the two-stage motor-compressor illustrated by Fig. 5, itincludes, on the one hand, a central motor cylinder 28, with inlet ports29 (the exhaust ports are not shown), and, on the other hand, on eitherside of the machine, a low pressure compressor cylinder 30, a highpressure cylinder 3i (the valves of these cylinders and the conduitsthrough which they are connected are not shown by the drawings), and amovable system including a motor piston 32, a low pressure compressorpiston 33 and a high pressure compressor piston 3l, the two movablesystems located on either side of the machine, respectively, and whichmove in opposite directions, being connected together, in the knownmanner, through suit.

able synchronizing means (not shown by the drawing).

I further provide, on either side of the machine, a return energyaccumulator the air cushion of which is housed in a hollow cylindricalportion of piston 32 carried by crown 5c and extending on the outer sidethereof.

According to the invention, I provide the above mentioned baille forminga communication passage near the crown 5c of the piston and constitiltedby a partition 3S, for instance in 'the shape of a nozzle. This bailledivides the inside of the energy accumulator air cushion into twoportions, one of which, d, has a constant volume, while the other, e,has a variable volume, the communication between these two parts takingplace through the restricted section aperture 3'! formed in partition36.

In this way, I obtain, during the displacements of the pistons, an airstream which, during the outward strokes thereof, flows from part etoward part d, and in the opposite direction during the inward strokesof the pistons. I thus obtain an intensive cooling of the crown 5c ofmotor piston-32.

According to another feature of my invention,

' instead of evacuating to the outside the calories absorbed by the airof the cushion exclusively through the wall of cylinder 9, I provide,inside said cushion, cooling means, for instanceconstituted by a coil3l, with a cooling water inlet 38 and outlet 4i).v Preferably, coil 38,iixed with its cooling water inlet and outlet on the outer end wall i2,extends inside the piston (see Figs. 2 to 5) Y In aseneral manner, whileI have. in the above description, disclosed what I deem' to be What Iclaim is:

l. A free piston machine which comprises, in combination, a motorcylinder, a motor piston reely movable in said cylinder including acrown nd a cylindrical hollow portion extending out- `ardly from saidcrown, means for accumulating, dr ring every outward stroke of saidpistons, en-

side at least one of said pistons, and cooling tins ergg for producingthe next inward stroke thereof, I

said last mentioned means including a gas cushion at least partlycontained in the hollow portion of said piston, and a tube having itsouter wall at a distance from the inner wall of said cylindrical portionof the piston, carried by said piston and extending inwardly to a shortdistance of said crown, said tube being interposed between a part ofsaid cushion located inside said piston and the remainder of saidcushion.

2. A free piston machine which comprises, in combination, a motorcylinder, a motor piston freely movable in said cylinder including a,crown and a cylindrical hollow portion extending outwardly from saidcrown, means for accumulating,

during every outward stroke of said pistons, energy for producing thenext inward stroke thereof, said last mentioned means including a gascushion at least partly contained in the hollow portion of said piston,a tube having its outer wall at a distance from the inner wall of saidcylindrical portion of the piston, carried by said piston and extendinginwardly to a short distance of said crown, said tube being interposedbetween a part of said cushion located inside said piston and theremainder of said cushion, and cooling fins carried by the inner wall ofsaid piston about the inner end of said tube.

3. A free piston machine which comprises, in combination, a motorcylinder, a motor piston freely movabl in said cylinder including acrown and a cylindrical hollow portion extending outwardly from saidcrown, a hollow piston carried by said cylindrical portion around theouter end thereof, means on the outer side of said last mentioned pistonforming therewith a variable vol,- ume chamber, means for accumulating,during every outward stroke of said pistons, energy for producing thenext inward stroke thereof, said last mentioned means including a gascushion at least partly contained in the hollow portions of said pistonsand said variable Volume chamber,

and a tube having its outer wall at a distance i from the inner wall ofsaid cylindrical portion of the motor piston, carried by said pistonsand extending inwardly to a short distance of said crown, said tubebeing interposed between said variable volume chamber and a part of saidcushion located inside at least one of said pistons.

4. A free piston machine which comprises, in

combination, a motor cylinder, a motor piston freely movable insaidcylinder including a crown and a cylindrical hollow portionextending outwardly from said crown, a hollow piston carried by saidcylindrical portion around the outer end thereof, means on the outerside of said last mentioned piston forming therewith a variable volumechamber, means for accumulating, during every outward stroke of saidpistons, energy for producing the next inward stroke thereof, said lastmentioned means including a gas cushion at least partly contained in thehollow portions of said pistons and said variable volume chamber, a tubehaving its outer wall at a distance from the inner wall of saidcylindrical portion of the motor piston, carried by said pistons andvextending inwardly to a short distance of said crown, said tube beinginterposed between said variable volume carried by the inner wall ofsaid motor piston about the inner end of said tube.

5. A free piston machine which comprises, in combination, a motorcylinder, a motor piston ,freely movable in said cylinder including acrown and a cylindrical hollow portion extending outwardly from saidcrown, a hollow piston carried by said cylindrical portion around theouter end thereof, the spaces inside said two pistons being incommunication, means on the outer side of said last mentioned pistonforming therewith a variable volume chamber, means for vaccumulating,during every outward stroke of said pistons, energy for producing thenext inward stroke thereof, said last mentioned means includ- 'ing a gascushion at least partly contained in the hollow portions of -saidpistons and said variable volume chamber, and tube having its outer wallat a distance from the inner wall of said cylindrical portion of themotor piston, carried by said last mentioned piston and extendinginwardly to a short distance-of said crown, said tube opening at itsouter end into said variable volume chamber and at its inner end intothe space inside said motor piston close to said transverse wallthereof.

6. A free piston machine which comprises, in combination, a motorcylinder, a motor piston freely movable in said cylinder including a.crown and a cylindrical hollow portion extending outwardly from saidcrown,- a hollow piston carried by said cylindrical portion around theouter end thereof, means on the outer side of said last mentioned pistonforming therewith a variable volume chamber in communication with theinside of said second mentioned piston, means for accumulating, duringevery outward stroke of said pistons, energy for producingthe nextinward stroke thereof, said last mentioned means including a gas cushionat least partly contained in the hollow portions of said pistons andsaid variable volume chamber, and a tube having its outer wall at adistance from the inner wall of said cylindrical portion of the motorpiston, carried by sald thereof, means on the outer side of said lastmentioned piston forming therewith a variable volume chamber incommunication with the inside of said second mentioned piston, means foraccumulating, during every outward stroke of said pistons,

energy for producing the next inward stroke thereof, said last mentionedmeans including a gas cushion at least partly contained in the hollowportions of said pistons and said variable volume chamber, a tube havingits outer wall ata distance from the inner wall of said cylindricalportion of the motor piston, carried by said last mentioned piston andextending inwardly to a short distance of said crown, said tube openingat its outer end intol said variable volume chamber and at its inner endinto the space inside said motor piston close to said transverse wallthereof, and a transverse annular partition between the outer wall ofsaid tube and the inner wall of said cylindrical hollow portion of themotor piston, at an intermediate point of said tube, thus dividing theannular space between said tube and said portion of the-motor pistoninto two compartments, the outer one of which is in communication withsaid variable volume chamber.

8. A free piston machine which comprises, in combination. a motorcylinder, a motor piston freely movable in said cylinder including acrown and a cylindrical hollow portion extending outwardly from saidcrown, means for accumulating,

during every outward stroke of said pistons, energy for producing thenext inward stroke thereof, said last mentioned means including a gascushion atleast partly contained in the hollow portion of said piston, atube having its outer wall at a distance from the inner wall of saidcylindrical portion of the piston, carried by said piston and extendinginwardly to a short distance of said crown, said tube being interposedbetween a part of said cushion located inside said piston and theremainder of said cushion, and a coil for circulation of cooling liquidmounted inside said hollow portion of the motor piston.

9. A free piston machine which comprises, in combination, a motorcylinder, a motor piston freely movable in said cylinder including acrown and a cylindrical hollow portion extending outwardly from saidcrown, means for accumulating,

during every outward stroke ofsaid pistons, energy for producing thenext inward stroke thereof, said last mentioned means including a gascushion at least partly contained in the hollow portion of said piston,a tube having its outer wall at a distance from the inner wall of saidcylindrical portion of the piston, carried by said piston and extendinginwardly to a short distance of said crown, said tube being interposedbetween a part of said cushion located inside said piston and theremainder of said cushion, and a coil for circulation of cooling liquidmounted inside said tube. Y

10. A free piston machine which comprises, in combination, a motorcylinder, a motor piston freely movable in said cylinder and including acrown and a cylindrical hollow portion carried by said crown on theouter side thereof and having its axis at right angles to the generalplane of said crown, means for accumulating energy during every outwardstroke of said piston toA produce the next inward stroke thereof, saidmeans including said cylindrical hollow portion of the piston, a partrigid with said cylinder arranged to form with`said cylindrical hollowportion a chamber of a volume variable during the `reciprocatingmovement of said piston and a vcrown and a cylindrical hollow portioncarried by said crown on the outer side thereof and having its axis atright angles to thegeneral plane of said crown, means for accumulatingenergy during every outward stroke of said piston to produce the nextinward stroke thereof, said means including said cylindrical hollowportion of the piston, apart rigid with said cylinder arranged to formwith said cylindrical hollow portion a chamber of a volume variableduring the reciprocating movement of said piston and a mass of gaspermanently enclosed in said chamber. and a baille rigid with saidcylindrical hollow portion of the piston, said baflle being arranged toleave between a portion of said chamber adjoining said crown and theremainder of said chamber a restricted passage located close to saidcrown.

arranged to form with said cylindrical hollow portion a chamber of avolume variable duringI the reciprocating movement of said piston, amass of gas permanently enclosed in said chamber, and a baille rigidwith one of the two last mentioned parts which form together saidvariable volume chamber, said baille being arranged to leave between aportion of said chamber adjoining said crown and the remainder of saidchamvber a restricted passage located close to said crown, and a coilfor circulation df cooling liquid provided in said chamber.

13. A free piston machine which'comprises, in combination, a motorcylinder, a motor piston freely movable in said cylinder and including acrown and a cylindrical lhollow portion carried by said crown on theouter side thereof and having its axis at right angles to the generalplane of said crown, means for accumulating energy during every outwardstroke of said piston to produce the next inward stroke thereof, saidmeans including said cylindrical hollow portion of the piston, a partrigid with said cylinder arranged to form with said cylindrical hollowportion a chamber of a volume variable during the reciprocating movementof said piston, a mass of gas permanently enclosed in said chamber, anda baille rigid with one of the two last mentioned parts which formtogether said variable volume chamber, said baille being arrangedtoleave between a portion of said chamber adjoining said crown and theremainder of said chamber a restricted passage located close to saidcrown, and a coil for circulation of cooling liquid provided in saidhollow portion of said piston.

ROBERT HUBER.

REFERENCES CITED The following .references are of record in the le ofthis patent:

`UNIIIED STATES PATENTS Number Name Date 1,628,652 Carlson May 17, 19272,007,305 -Pescara July 9, 1935 2,150,740 Y Hammersmith Mar. 14, 19392,178,310 Y Pescara Oct; 31, 1939 2,282,085 Nichols et al. May 5, 1942Moore Feb. 20, 1945

